This study is part of the program project Molecular Regulation of Muscle Glucose Metabolism in Man; its overall purpose is to establish a system for determining how changes in plasma glucose and insulin concentrations regulate mRNA abundance, protein levels, and activities for two key enzymes in skeletal muscle glucose metabolism. This protocol proposes to determine how acute exercise and physical training alter GS, HKI, and HKII activities, protein content and mRNA levels in skeletal muscle.